First of all, the cosmetic changes. While in the landscape orientation, Dropbox offers the same split view that Mail and several others use. Pictures and documents look great and legible on the large screen. Across the toolbar are icons to jump to your favorites, adjust your account settings, email a public link to a file (or copy it to the clipboard), mark a file as a favorite and finally choose an app to open a file.
In portrait orientation the sidebar disappears and you're left with a full-screen view of your document and a few icons at the top. It looks super.
I flipped through a multi-page PDF document as if it lived on my iPad, then sent it to GoodReader just as easily (for the record, GoodReader can also access your Dropbox files directly). Other apps that handle PDFs include QuickOffice and Air Sharing HD. You say you don't have any of those apps? No problem. Dropbox will suggest apps that support a given document type, complete with icon, brief description and purchase link.
It gets better: Microsoft Office docs (.doc/docx, .xls/xlsx, .ppt/pptx) can be sent to their corresponding iWork apps for editing. I took a huge PPT file from Dropbox (about 400 slides), sent it to Keynote, and it opened right up, looking good.
The new build is a solid update that makes Dropbox a pleasure to use on the iPad. The UI is uncluttered, files look great (especially in portrait mode) and it's simple to send a file to your favorite app. What's not to love?
If Dropbox doesn't float your boat, check out Pogoplug (and its accompanying iPhone app), a USB NAS adapter that gives you network access to your data from home and on the road.